Not a clean label ingredient

Diacetyl

Also known as: butanedione, Acetoin

Diacetyl (butanedione or butane-2,3-dione) is an organic compound with the chemical formula (CH3CO)2. It is a yellow/green liquid with an intensely buttery flavor. A natural byproduct of the fermentation process and occurs naturally in foods such as coffee, alcoholic beverages, and cheese.